Negative Sequence Power based Fault Detection Scheme for Power Islands during Unbalanced Faults

High penetration of inverter interfaced distributed generators (IIDGs) in the distribution network has evolved the concept of power islands, which can operate independently to feed the local network when the grid is unavailable. The unconventional fault signatures of IIDGs adversely affect the conventional protective relaying. The low short circuit current contribution and control dependent fault behavior of inverters creates protection challenges mainly for these power islands. This article unveils the failure of phase and sequence components based on conventional fault detection schemes in the presence of IIDGs. To address this issue, a negative sequence power based fault detection method is proposed, which only requires local voltage and current at the relaying point, hence does not depend upon any type of communication. The scheme is validated on islanded 18-bus CIGRE benchmark network for various fault cases at different inception angles for various fault resistances and load variations. Further, the proposed scheme is also tested for no-fault scenarios such as motor starting transient, load imbalance, and IIDG outage.